adds color profiles/output intents and an xmp metadata stream to the document in order to be compliant with pdf/a-1b (basic). this compliance level is toggled on the builder since it will generate larger files and set to 'off/none' by default. pdf/a documents are also not able to use standard fonts so using a font when the compliance level is not none will throw.
after we split the solution into multiple projects the xml doc comments were no longer packed in the generated nuget package. in addition they were only generated for the net standard 2.0 target framework.
this change generates comments for all target frameworks and makes sure they're included in the generated package. it also adds missing doc comments where they weren't included on the public api and clears up a couple of minor formatting issues in the affected files.
in order to include all projects from the solution we create a new solution with an entry-point assembly which references all projects. calling dotnet pack on this single project then packages all assemblies into the produced nuget package.
also remove old glyph list references from the main project since they have moved to the fonts project.
by default nuget pack does not include project dependencies. this is suboptimal since it would require managing at least 5 nuget packages. this uses a workaround detailed here https://github.com/nuget/home/issues/3891 to copy the dependent dlls to the generated nuget package. this doesn't resolve the issue of how we publish the documentlayoutanalysis project, since it is the top of the dependency tree and we publish its parent, rather than it.
to make the project more useful and expose more usable classes we're rearchitecting in the following way. code used to read fonts from external file formats like truetype, adobe font metrics (afm) and adobe type 1 fonts are moving to a new project which doesn't reference most of the pdf logic. the shared logic is moving to a new flat-structured project called core. this is a sort-of onion type architecture, with core being the... core, fonts being the next layer of the onion, pdfpig itself the next. this will then support additional libraries/projects as outer layers of the onion as well as releasing standalone version of the font library as pdfbox does with fontbox.
support both xobject and inline images. adds unsupported filters so that exceptions are only thrown when accessing lazily evaluated image.bytes property rather than when opening the page.
treat all warnings as errors.
package license url is deprecated in favour of package license expression but nuget doesn't seem to support expressions properly for published packages yet so we'll keep the deprecated url for the time being. having both url and expression causes the build to fail.
small obvious performance improvements for file header passing and getting the encoding information using the existing reverse name to code map.
temporary 'safe' untested implementation of seac for type 1 charstrings.
make structure public
bump version of package and project to 0.0.3 (it had accidentally increased to 0.0.5)
